Pre-select the first facet choice when this choice is different on each page the facet is on

<?php 
// Pre-select the first facet choice when this choice is unknown / different on each page the facet is placed on
// To pre-select a know choice, use the 'facetwp_preload_url_vars' hook instead:
// https://facetwp.com/help-center/developers/hooks/querying-hooks/facetwp_preload_url_vars/

add_action( 'facetwp_scripts', function() {
  ?>
  <script>
    document.addEventListener('facetwp-refresh', function() {
      if ( !FWP.loaded ) { // Only on first page load
        var facet_name = 'my_facet_name';  // Change 'my_facet_name' to the name of your facet
        if ( 'object' == typeof FWP.facets[facet_name] && 1 > FWP.facets[facet_name].length ) {
          var temp = document.createElement('div');
          temp.innerHTML = FWP_JSON.preload_data.facets[facet_name];
          var first = temp.getElementsByClassName('facetwp-radio'); // for a Radio facet, change if needed
          first = first[1]; // Pre-select the second choice, skips the first "Any" choice. Use first[0] if there is no "Any" choice
          FWP.facets[facet_name] = [ first.getAttribute('data-value') ];
          FWP.loaded = 1; // force TRUE to make an AJAX request & populate results
        }
      }
    });
  </script>
  <?php
}, 100 );


// Alternative: Pre-select using a page refresh with window.location.href instead of facet refresh

add_action( 'facetwp_scripts', function() {
    ?>
      <script>
        document.addEventListener('facetwp-refresh', function() {
            if ( !FWP.loaded ) {
                var facet_name = 'my_facet_name';  // Change 'my_facet_name' to the name of your facet
                if ( 'object' == typeof FWP.facets[facet_name] && 1 > FWP.facets[facet_name].length ) {
                    var temp = document.createElement('div');
                    temp.innerHTML = FWP_JSON.preload_data.facets[facet_name];
                    var first = temp.getElementsByClassName('facetwp-radio'); // for a Radio facet, change if needed
                    first = first[1]; // Pre-select the second choice, skips the first "Any" choice. Use first[0] if there is no "Any" choice
                    FWP.facets[facet_name] = [ first.getAttribute('data-value') ];
                    let qs = FWP.buildQueryString();
                    let href = window.location.href
                    let prefix = (-1 < href.indexOf('?')) ? '&' : '?';
                    window.location.href = href + prefix + qs;
                }
            }
        });
      </script>
    <?php
}, 100 );